The present invention is related to an improved high efficiency heat condensing furnace or heat exchanger of the type disclosed in U.S. Pat. Nos. 4,311,191 and 4,311,192, each issued on Jan. 19, 1982 in the name of Gerry Vandervaart, as well as other improvement patents also issued in the name of Gerry Vandervaart under U.S. Pat. Nos. 4,420,034; 4,429,734; 4,442,890; 4,415,023; 4,441,546; 4,458,665; 4,461,345; and 4,825,664. The contents of these patents, particularly the first two and the last, are incorporated herein by reference particularly with respect to presently conventional structural and functional characteristics of such prior art heat exchangers or condensing furnaces which are, obviously, compatible with the condensing furnace of the present invention. U.S. Pat. Nos. 4,311,191 and 4,311,192 each disclose a heat exchanger which includes conventional components such as a compressor, indoor and outdoor coils, blowers associated with the coils, one or more reversing/expansion valves and appropriate tubing or conduits such that the heat-exchange medium/refrigerant (Freon) can flow in opposite directions through associated conduits during the air conditioning/cooling mode of operation on the one hand and the heating or heat augmenting modes of operation on the other.
These conventional heat exchangers operate in the heat-augmenting mode through the ignition of a gas burner which provides a very intense flame in a combustion chamber within an outdoor A-coil. Such conventional heat exchangers are extremely efficient up to approximately five (5) tons, and this efficiency is attributed primarily to the fact that the outdoor A-coil is relatively short in height (20 inches high), and the relatively intense heat of the flame is "trapped" within the confines of the A-coil. Though the efficiency is extremely high, the A-coil can become damaged because of the intense heat of the flame primarily because the aluminum fins of the A-coil cannot conduct heat to the copper tubes passing therethrough (conducting the refrigerant) as fast as the aluminum fins absorb the heat from the flame. At the moment of combustion, the flame generated by the burner within the combustion chamber of the A-coil reaches a temperature of approximately 2200.degree. F. If complete combustion and absorption is not achieved, the efficiency drops and unburned gas will escape into the atmosphere. However, if the heat/Btu's are absorbed by the aluminum fins faster than the fins can conduct the heat therethrough and to the copper tubing, the coils will dry out creating an acidic condition which deteriorates the aluminum fins reducing the efficiency and life thereof. Under optimum conditions, the A-coil should absorb all of the heat from the flame as immediately as possible causing the flue gases to cool and condense so that the condensation on the aluminum fins of the A-coil prevents deterioration thereof. Under this optimum condition, the flame is absorbed through the condensation which keeps the exterior of the aluminum fins "wet", prevents drying and acidic deterioration, and assures high efficiency because of maximum Btu absorption and A-coil life.
Obviously, one way to achieve absorption in the absence of drying out of the coil and preventing damage to the aluminum fins thereof would be to minimize the heat of the flame. However, if the heat of the flame were reduced, the output of the overall condensing furnace would be reduced. Accordingly, desirably an optimum condition is that of maintaining the flame at maximum intensity in conjunction with a relatively small A-coil which can absorb the heat from the flame and transfer the heat as fast as it is absorbed to achieve efficiency, yet do so without drying the aluminum fins of the coil. In other words, the intense heat of the flame must be absorbed and cooled such that the flue gases are cold enough to allow condensation to form on and wet the coil and prevent deterioration thereof.